332 research outputs found

    Indecomposable modules and Gelfand rings

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    It is proved that a commutative ring is clean if and only if it is Gelfand with a totally disconnected maximal spectrum. Commutative rings for which each indecomposable module has a local endomorphism ring are studied. These rings are clean and elementary divisor rings

    Fast Reduction of Bivariate Polynomials with Respect to Sufficiently Regular Gröbner Bases

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    International audienc

    Believability of cigarette warnings about addiction: National experiments of adolescents and adults

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    Introduction: We conducted two experiments to examine the believability of three addictionfocused cigarette warnings and the influence of message source on believability among adolescents and adults in the United States. Methods: Experimental data were collected using national phone surveys of adolescents (age 13-17; n = 1125; response rate, 66%) and adults (age 18+; n = 5014; response rate, 42%). We assessed the believability of three cigarette warnings about addiction attributed to four message sources (Food and Drug Administration [FDA], Surgeon General, Centers for Disease Control and Prevention [CDC], no source). Results: The majority of adolescents and adults reported the three cigarette warnings were very believable (49%-81% for adolescents; 47%-76% for adults). We found four to five times higher odds of adolescents believing a warning that cigarettes are addictive (warning 1) or that nicotine was an addictive chemical (warning 2) compared to a warning that differentiated the addictive risks of menthol versus traditional cigarettes (warning 3), warning 1 adjusted odds ratio (aOR): 4.53, 95% confidence interval (CI): 3.10, 6.63; warning 2 aOR: 3.87, 95% CI: 2.70, 5.50. Similarly, we found three to five times higher odds of adults (including current smokers) believing the same warnings, warning 1 aOR: 3.74, 95% CI: 2.82, 4.95; warning 2 aOR: 3.24, 95% CI: 2.45, 4.28. Message source had no overall impact on the believability of warnings for either population. Conclusions: Our findings support the implementation of FDA's required warnings that cigarettes are addictive and that nicotine is an addictive chemical. These believable warnings may deter adolescents from initiating smoking and encourage adults to quit smoking. Implications: This article describes, for the first time, the believability of different cigarette warnings about addiction. We now know that the majority of adolescents and adults believe cigarette warnings that highlight cigarettes as addictive and that nicotine is an addictive chemical in tobacco. However, a warning that highlighted the relative risk of addiction for menthol cigarettes compared to traditional cigarettes was not as believable among either population. Our findings support the implementation of FDA's required warnings that cigarettes are addictive and that nicotine is an addictive chemical that may deter adolescents from initiating smoking and encourage adults to quit smoking

    She’s so vain? A Q Study of Selfies and the curation of an online self.

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    Selfie posting is now a well-established practice, particularly for young women. However, it is nevertheless much maligned in popular discourses. As a counterpoint to digital narcissism, selfie posting is also constituted as relational. This Q methodological study explored how young women make sense of selfie practices. Twenty-seven young women aged 18-23 sorted a set of statements about selfies into a quasi-normal grid. These sorts were factor analysed to identify shared patterns. Four factors were identified which were subsequently analysed qualitatively, producing a narrative for each. These included, (1) ‘Presenting…Me!’ (2) ‘I am what I am’, (3) ‘Sharing is caring’ and (4) ‘The In-crowd – beautiful and popular’. The complexity of identity curation evidenced in this study highlights the importance of moving beyond both polarised characterisations and the pathologisation of young women selfie takers in order to explicate the interplay between normative femininities and the digital self

    The homotopy type of the loops on (n1)(n-1)-connected (2n+1)(2n+1)-manifolds

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    For n2n\geq 2 we compute the homotopy groups of (n1)(n-1)-connected closed manifolds of dimension (2n+1)(2n+1). Away from the finite set of primes dividing the order of the torsion subgroup in homology, the pp-local homotopy groups of MM are determined by the rank of the free Abelian part of the homology. Moreover, we show that these pp-local homotopy groups can be expressed as a direct sum of pp-local homotopy groups of spheres. The integral homotopy type of the loop space is also computed and shown to depend only on the rank of the free Abelian part and the torsion subgroup.Comment: Trends in Algebraic Topology and Related Topics, Trends Math., Birkhauser/Springer, 2018. arXiv admin note: text overlap with arXiv:1510.0519

    Branch Rings, Thinned Rings, Tree Enveloping Rings

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    We develop the theory of ``branch algebras'', which are infinite-dimensional associative algebras that are isomorphic, up to taking subrings of finite codimension, to a matrix ring over themselves. The main examples come from groups acting on trees. In particular, for every field k we construct a k-algebra K which (1) is finitely generated and infinite-dimensional, but has only finite-dimensional quotients; (2) has a subalgebra of finite codimension, isomorphic to M2(K)M_2(K); (3) is prime; (4) has quadratic growth, and therefore Gelfand-Kirillov dimension 2; (5) is recursively presented; (6) satisfies no identity; (7) contains a transcendental, invertible element; (8) is semiprimitive if k has characteristic 2\neq2; (9) is graded if k has characteristic 2; (10) is primitive if k is a non-algebraic extension of GF(2); (11) is graded nil and Jacobson radical if k is an algebraic extension of GF(2).Comment: 35 pages; small changes wrt previous versio

    Locked and Unlocked Polygonal Chains in 3D

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    In this paper, we study movements of simple polygonal chains in 3D. We say that an open, simple polygonal chain can be straightened if it can be continuously reconfigured to a straight sequence of segments in such a manner that both the length of each link and the simplicity of the chain are maintained throughout the movement. The analogous concept for closed chains is convexification: reconfiguration to a planar convex polygon. Chains that cannot be straightened or convexified are called locked. While there are open chains in 3D that are locked, we show that if an open chain has a simple orthogonal projection onto some plane, it can be straightened. For closed chains, we show that there are unknotted but locked closed chains, and we provide an algorithm for convexifying a planar simple polygon in 3D with a polynomial number of moves
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